Softening water



20 ly be used in softening water.

Patented Aug. 1, 1933 SOFTENING WATER Otto Liebknecht, Neubabelsberg,Germany, as signor to The Permutit Company, New York, N. Y., aCorporation of Delaware No Drawing. Application September 16, 1931,Serial No. 563,231, and in Germany December '7 Claims. (Cl. 21024) Thisinvention relates to softening water; and it comprises a process whereinsalt-treated serpentine is alternately used for softening water bycontact therewith and is regenerated by a solution of common salt, theserpentine being sometimes activated by a previous treatment withvarious chemicals; all as more fully hereinafter set forth and asclaimed.

It is the usual assumption that base exchange to any useful extent is aspecific property of the zeolites or hydrated alumino-silicates andcertain cognate minerals, particularly glauconite. {The exchange poweris supposed to be in some way connected with the particular chemicalstructure characterizing the alumino-silicates.

I have however found that useful base exchange actions are exercised byquite another class of minerals; those mineralogically known as theserpentine class and that they can advantageous- They are hydratedsilicates of magnesia, although as minerals they often contain minoramounts of other bases replacing magnesia;.ferrous oxid, lime and,sometimes, nickel oxid. Minor proportions of alu- 5 mina are oftenpresent. The serpentines are probably, at least sometimes, alterationproducts of minerals of the types of olivine and pyroxene.

Serpentine may occur in massive, lamellar, foliated, fibrous orcrystalline form. Some of the fibrous forms, such as chrysotile, are onthe market'as asbestos. Not all commercial asbestos" is-serpentine, butmuch of it is. For the present purpose, the massive or rocky forms ofserpentine, which can be converted into granules of the size of thoseordinarily used in a softener, are deemed best, as they enable the useof the ordinary type of softener, upfiow or downflow, without changes inconnections. However, fibrous forms may be used and enable theemployment of new types of softener.

Most of the minerals of the serpentine group are useful for the presentpurposes. Meerschaum, soapstone, talc and the like may be used. There'issome advantage in the use of the less pure forms of serpentine, thosecontaining other bases than magnesia, such as ferric or ferrous oxid andalumina. When a mineral containing nickel oxid is available, it is welladapted for my purposes. One typical serpentine which I have 50 foundavailable contains 2 to 11 per cent of iron oxid and 0.5 to 3 per centalumina.

Since serpentine is a hydrated silicate of magnesia, it is somewhatunexpected that it should be available for general use in softening hardwater, in which part of the hardness is often due to magnesia. It is,however, a fact that serpentine can be used for softening such water.

In a specific embodiment of the present invention, utilizing the impureserpentine rock mentioned containing a little iron oxid and a minor 0amount of alumina, granulated rock was treated with a common saltsolution to provide it with exchangeable base. The fibrous, dark olive,granulated, salt-treated mineral, in suitable grain size, used in anordinary softener evinced an exchange 5 power equivalent to 0.4 to0.5-per cent 020, this exchange power remaining constant after long usein softening water with alternate softening and regeneration. Themineral proved resistant to water containing a-high percentage of carbondioxid. Q

While the serpentine can be used in the raw condition with merely aprior treatment with common salt, the exchange power can be increasedsomewhat without detriment to the physical qualities, by varioustreatments additional to the treatment with common salt, as, forinstance, with a solution of an alkali silicate, of an alkali carbonate,or of a caustic alkali. These solutions improve the activity of thesurso face of the granules. Activation can also be secured with acidreacting solutions, that is, those developing acid by hydrolysis andacid to test paper, such as solutions of iron, aluminum and chromiumsalts. Mild actual acidity, such 35 as that of an alkali bisulfatesolution or of highly dilute hydrochloric acid, is also useful inactivating. Alternate treatments with alkaline reacting solutions andacid reacting solutions, are also useful. A treatment with common saltmay be intercalated. In one specific way of treating serpentine, Itreated the serpentine with waterglass solution, washed and then treatedwith a solution of aluminum sulfate. Iron chlorid could have have beensubstituted for the aluminum sulfate. The order of treatments can bereversed.

In one specific example of improving serpentine by surface activation, afibrous slaty serpentine was granulated to a size passing a screen with140 meshes per square centimeter and held by a 900 mesh screen. Thegranules were immersed in a 3 per cent ferric chlorid solution. Theferric chlorid was then removed andthe granules washed. The washedgranules were then treated witha solution of waterglass made by dilutingcommercial sirupy silicate of soda with 10 times its weight of water.The silicate of soda solution was removed and the granules washed withneutral water. The washed granules were then treated with a common saltsolution to provide exchangeable base. After removing the salt solution,the product was ready for use at higher pressures. However, in the caseof acid solutions, high temperatures and high concentrations must beused with care to avoid breaking down the mineral.

Untreated raw serpentine sometimes, but not always, gives a turbidity tothe water for a few cycles when first used in a softener. The variouschemical treatments mentioned, in addition to increasing the exchangecapacity; also obviate this tendency toward giving turbid water. Thetendency may also be obviated by heating the serpentine under eitheroxidizing or reducing conditions at temperatures above 100 C. Thetemperature should not be carried sufficiently high to effect completedehydration and advantageously not above 300 to 500 C. Preheated mineralcan be subjected to the various activating processes described.

It is often desirable to remove from a water the bicarbonate orcarbonate radical in addition to eliminating the hardness or calcium andmagnesium. This can be accomplished by treating the minerals of thisserpentine group with an acid (such as sulphuric acid) thereby impartinga replaceable hydrogen ion. This hydrogen of the acid-treated serpentinereacts with the bicarbonate or carbonate of the water, whereby thisimparted by the acid treatment without appreciable disintegration of thegranules. This is a special advantage over other substances hithertoavailable for this purpose.

What I claim is:-

1. In softening water, the process which comprises alternately softeninghard water by contact with serpentine and regenerating said serpentineby contacting with a solution of sodium chlorid.

2. In the process of claim 1, employing a serpentine with activatedsurfaces.

3. In the process of,claim 1, employing a serpentine with surfacesactivated by an acid reacting solution.

4. In the process of claim 1, employing a serpentine with surfacesactivated by an alkaline reacting solution.

5. In the process of claim 1, employing a serpentine with surfacesactivated by both an acid reacting and an alkaline reacting solutionused in succession.

6. In the process of claim 1, employing a serpentine baked to resist thedisintegrating action of water.

7. In the process of claim 1, employing a baked serpentine havingactivated surfaces.

OTTO LIEBKNECHT.

